Conventional sensors for measuring physical acceleration typically have a micromechanical structure made of silicon (sensor core) and an electronic evaluation system. Sensor cores which make it possible to measure an acceleration in a direction orthogonal to a main plane of the sensor core are referred to as Z-sensors. Such sensors are used in the automobile sector, for example, in ESP systems, or in the mobile telephony sector.
The aforementioned sensor principle is, for example, discussed in greater detail in Chapter 6 of the dissertation “Surface micromechanics sensors as electric test structures for characterizing their manufacturing processes;” Maute, Matthias; University of Tübingen, Germany, 2003.
Patent document EP 0 244 581 discusses a micromechanical sensor for the purpose of automatic triggering of occupant protection devices.
Patent document EP 0 773 443 B1 discusses a micromechanical acceleration sensor.
Within the scope of the so-called “FP functionalization,” which, for example, is discussed in DE 10 2007 060 878 A1 and DE 10 2009 000 167 A1, a rocker is formed for the micromechanical acceleration sensor which is structured in two different silicon layers, rather than from only a single compact layer. Thus, movable “trough-shaped” structures may be formed.
When handling the acceleration sensor, in the event of a sudden overload (for example, if a control device including the acceleration sensor is dropped), the mass and thus the spring may be deflected in the vertical direction (i.e., out of plane). A mass of an FP functional layer may thereby pull out an upper electrode or the FP functional layer itself may also be destroyed.
In order to prevent this, mechanical stops have been provided, which are described, for example, in DE 10 116 931 A1. The stops described there block the rocker only after approximately 7 μm, up to approximately 10 μm. However, since, in the aforementioned technology having FP functionalization, the rocker is situated between the two electrodes and the electrodes are less than 2 μm from each other, this conventional overload protection is no longer sufficient. Therefore, additional structures have been configured which are able to stop the rocker before it reaches the stop. Such mechanical stops are discussed in DE 10 2009 029 095 A1 and U.S. Pat. No. 8,124,895 B2.